Ballater has many dining options to suit all pockets and details of most of them can be found on the Visit Ballater website in the Places to Eat section
www.visitballater.com
I particularly like Rocksalt and Snails and have eaten a light lunch there on a few occasions. We also had a great dinner at the Glen Lui Hotel before Christmas and use the Phoenix Chip Shop from time to time.
A new restaurant yet to feature on the site I mentioned is the Rothesay Rooms. The site for the restaurant and Highgrove Shop was donated by the Co-operative Group for a peppercorn rent and converted by The Great Steward of Scotland’s Dumfries House Trust Outreach Programme, a charity chaired by HRH Prince Charles, The Prince of Wales or The Duke of Rothesay as he is known in Scotland.
The restaurant aims to provide a new amenity for the local community and stimulate local commerce and tourism following the devastating floods brought in by Storm Frank at the end of December 2015, which destroyed more than 300 homes and 60 businesses in the village. You don't have to look far on the internet to discover how much damage was done to Ballater at the time, but since then a great deal of hard work has gone in to revitalising the village and it is very much open for business.
https://rothesay-rooms.co.uk/
I don't know how long you have to spend in Ballater but if you have the opportunity to range a little further afield I would certainly recommend Finzean Farm Shop for a good lunch. It is near Banchory and if you are travelling that way might be a convenient place for lunch, morning coffee or afternoon tea.
http://finzean.com/default.html
Also if you are in Braemar then I certainly recommend The Bothy for lunch or a snack. We like it a lot and eat there a couple of times a month. In fact we are going there on Monday for lunch. The Bothy doesn't have a website, but it does have a Facebook page
https://en-gb.facebook.com/The-Bothy-Braemar-1536437353245804/
I think it is fair to say that there is a very strong ethos among the restaurants, coffee shops and other eateries in the Ballater area to provide good quality food with as much as possible sourced from local suppliers.
I live in Crathie which is only eight miles along the A93 from Ballater and know the area very well. If there are any further questions which you have or if there's anything I can help you with then feel free to send me a private message if you wish.